1. Field of the Invention
This invention generally relates to optical equipment for assessing the performance and alignment of optical components and systems and, more particularly, to apparatus for presenting object targets over a wide field of a test optic to assess its optical performance where the field of the test optic is commensurate with that at which it is intended for use.
2. Background of the Prior Art
To assess the performance (e.g., focus, MTF, sharpness, field tilt, alignment) of an optical system, such as a cell phone camera or automotive camera, one can place a target in front of the system and directly examine the image formed by the lens or, in the case of a camera, assess the quality of the image produced by the camera.
Such targets are typically spaced from the lens or camera at distances corresponding to the use of the product. In the case of a cell phone camera, the object may be placed in the range of a few inches to several meters away. It is straight forward to place a target near the camera. Placing a target at or beyond the hyperfocal distance of the camera or lens may require placement of the target several meters away. If the field of view of the camera or lens is substantial, the target can grow quite large in size. For instance, for a camera or lens with a field of view of +/−40 degrees, the target needs to be 2 times the tangent of 40 degrees (1.67) times the object distance. For this example, the Target Size=2*Distance*tan(half-angle), for a 40 degree half angle and a 1 meter distant object, then the target size is: Target Size=2*(1 m)*tan(40 degrees)=1.67 meters.
So, for an object distance of 1 meter, the target would be 1.67 meters across. This large size constrains the footprint of the test equipment, and it is desirable to minimize the floor space requirements for such test equipment. Furthermore, testing wide field lenses and extreme field of view lenses, like fisheye lenses, requires even larger targets that are simply impractical to use in a manufacturing environment.
Consequently, it is a principle object of this invention to provide a compact system that can present multiple object targets over a wide field to an optical system or electro-optical system (e.g., a camera) to allow assessment of the performance or alignment of the optical or electro-optical system over its intended field and conjugate(s) of use.
Other objects of the invention will be obvious or will appear hereinafter when the following detailed description is read with the accompanying drawings.